Limited depth of field is a common problem in imaging devices such as conventional light microscope. Objects imaged in such cases are sharply in focus over a limited distance known as the depth of field. The Depth of field (DOF) is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image. Typically sharpness decreases with depth resulting in blurriness in at least some part of the image. Also, in order to capture a large amount of light from a small specimen under the imaging device, one needs to have a high numerical aperture. However, high numerical aperture results in a very shallow depth of field, due to which it is not possible to have all region of the scene to be in focus.
To improve the depth of field in a captured image, one or more digital image processing techniques may be employed. Using the digital image processing techniques, images taken at different depths of field of the same scene may be combined to produce a single composite image. The digital image processing techniques involve capturing multiple images of the same scene to form an image stack, identifying focused part from multiple images in the stack and recreating a single image with better depth of field by combining the focused parts. During the digital processing process, index information of the images in the stack is collected and processed to generate a depth map and composite image or/and a 3D model of the scene.
Typically, greater the number of images in the image stack greater is the DOF in the composite image. Though with the increase in number of images in the stack, the complexity, time required for processing the images, errors in the composite image and memory requirement also increases. There are many processing techniques which provide solutions to improve the depth of field. However, the known solutions have one or the other drawback such as misalignment of the images in the stack, illumination variations in the composite image, noises in the Depth map and composite image, low quality of the composite image with blotchy background, edge shadowing and depth cross over time complexity of the processes involved in depth of field calculations too many manually configurable parameters and unable to manage large image stacks.
Therefore, there is a need to have an improved method and system for digital image processing that may address at least one of the above mentioned limitations.